High current injection effects of the switching JFETs in the current electrometers

The performance of JFET as a switch in the feedback loop of a multigain ranging current electrometer is described. The study indicates that the electrometer starts departing from linear behavior as the input current becomes comparable to the drain saturation current of the JFET. It is shown that the nonlinearity in the electrometer behavior is attributable to the variations occurring in the ON resistance and gate current of the JFET.